Many kitchen and commercial stoves now incorporate a self-cleaning feature in which the heat producing means can be activated to generate a very high temperature within the oven so as to produce substantially complete combustion of organic deposits upon the surfaces of the oven. Such temperatures frequently run as high as 380.degree. Centigrade and above.
To ensure against inadvertent opening of the oven door while the oven is at elevated temperatures, a manual latch has been employed to latch the oven door in closed position, thus requiring a physical act in addition to grasping the handle of the door. However, concerns for user safety have led to the incorporation of various additional elements for latching the door in closed position during the high temperature portion of the cleaning cycle. Some such devices have used electrical interconnections between a solenoid engagable with the latch mechanism and circuitry controlling the high temperature phase of the appliance, particularly in the instance of electric ovens. Another approach has been the incorporation of a bimetallic strip responsive to the temperature in the oven and effective to move a pawl into a blocking position with respect to the latch subassembly, thereby preventing its movement from latched position to unlatched position when the bimetallic strip is exposed to preselected elevated temperatures. A device of this type is disclosed and described in detail in Erickson U.S. Pat. No. 3,438,666 granted Apr. 15, 1969.
To compensate for the temperature lag generally experienced between the temperature in the oven and that in the recess in which the bimetallic strip is disposed and the time lag between exposure of the bimetallic strip to the reduced temperature and the resultant movement of the blocking pawl during the cooling portion of the cycle, Siegel U.S. Pat. No. 3,540,767 granted Nov. 17, 1970 discloses and describes a clutch assembly in the operative connection between the bimetallic strip and the blocking pawl. As the blocking pawl rotates towards blocking position, it stops at a preselected point representing less rotation than that which might be effected by the bimetallic strip during the full heating cycle and there then occurs slippage as the bimetallic strip continues to expand. When the bimetallic strip begins to cool, it immediately begins to effect movement of the blocking pawl, thus compensating for the temperature lag since the amount of relative slippage may be controlled for the temperature lag experienced in a particular oven by proper dimensioning of the parts.
However, it has been found that the temperature characteristics of ovens vary widely from manufacturer to manufacturer and even from model to model of the same manufacturer. As a result, a set point for limiting rotation of the blocking pawl established in the latch assembly may not be satisfactory from one oven to the next. Moreover, movement in the unblocking direction from this set point may effect rotation of the blocking pawl to a point where there will be an increased and undesired distance of movement required in the next cleaning cycle to effect blocking of the operating mechanism.
It is an object of the present invention to provide an improved latch for ovens and the like with a high temperature latching subassembly with means for adjusting the points at which movement of the locking pawl will commence and terminate so as to permit use of the latch assembly in ovens having different thermal conditions.
It is also an object to provide such a latch which may be simply and economically constructed, which may be readily adjusted and which is rugged and durable in operation.
Another object is to provide such a latch wherein both the total travel of the locking pawl and its initial and final positions may be simply and readily varied.